Our aim is to investigate whether reduced exercise capacity, increased respiratory drive and dyspnoea are linked to heightened sympathetic activation at rest and during exercise in patients with COPD. Furthermore, the effect of unloading the respiratory muscles by using non-invasive ventilation (NIV) will be assessed. Fifteen stable COPD patients without NIV will be matched to 15 healthy control subjects (with sufficient microneurography recording). Furthermore COPD patients on regular NIV will be studied. Each participant will undergo symptom limited bicycle exercise and a handgrip protocol. Microneurography will be used to quantify sympathetic activity by the transcutaneous registration of postganglionic sympathetic efferents.